title: When is coagulase-negative Staphylococcus bacteraemia clinically significant?
abstract: BACKGROUND
  Coagulase-negative staphylococci (CoNS) are common contaminants in blood cultures (BC). A prospective study of patients with ≥ 2 blood culture sets and at least 1 positive CoNS BC was performed to develop an algorithm to assist in determining the clinical significance of CoNS bacteraemia.
  
  
  METHODS
  A single reviewer examined the medical records of patients with CoNS bacteraemia (January-June 2010). The determination of clinical significance was made according to CDC/NHSN (US Centers for Disease Control and Prevention/National Healthcare Safety Network) criteria. To explore risk factors associated with clinical significance, a multivariate analysis was performed. The performances of various algorithms were then compared. An algorithm to assist in determining clinical significance was developed.
  
  
  RESULTS
  Two hundred and sixty-nine cases were included; 97 (36%) were considered clinically significant bacteraemia (CSB). Predictors of CSB in the multivariate analysis were: time to positivity < 16 h (odds ratio (OR) 4.540, 95% confidence interval (CI) 1.734-11.884), identification of Staphylococcus epidermidis (OR 4.273, 95% CI 2.124-5.593), central venous catheter (OR 4.932, 95% CI 2.467-9.858), > 2 CoNS-positive bottles from different BC sets (OR 1.957, 95% CI 1.401-2.733), and Charlson score ≥ 3 (OR 2.102, 95% CI 1.078-4.099). The algorithm with best sensitivity (62%) and specificity (93%) for determining clinical significance of CoNS included Charlson score ≥ 3, Pitt score ≥ 1, neutropenic patients, presence of central venous catheter, identification of S. epidermidis, and time to positivity < 16 h. The positive predictive value was 83% and the negative predictive value was 81% (likelihood ratio 8.87).
  
  
  CONCLUSIONS
  The use of this algorithm could potentially reduce the misclassification of nosocomial bloodstream infections and inappropriate antibiotic treatment in patients for whom a positive CoNS does not represent a CSB.
authors.affiliation: Servicio de MI-Infecciosas, Hospital Clínico Universitario Virgen de la Arrixaca, Madrid-Cartagena, El Palmar, Murcia, Spain. elisag@eresmas.net
authors.forename: Elisa
authors.initials: E
authors.lastname: García-Vázquez
authors.forename: Ana
authors.initials: A
authors.lastname: Fernández-Rufete
authors.forename: Alicia
authors.initials: A
authors.lastname: Hernández-Torres
authors.forename: Manuel
authors.initials: M
authors.lastname: Canteras
authors.forename: Joaquín
authors.initials: J
authors.lastname: Ruiz
authors.forename: Joaquín
authors.initials: J
authors.lastname: Gómez
mesh_terms: D000465:Algorithms; D000704:Analysis of Variance; D016470:Bacteremia / Q000097:blood / Q000453:epidemiology / Q000382:microbiology*; D005260:Female; D006760:Hospitalization; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D013030:Spain / Q000453:epidemiology; D013203:Staphylococcal Infections / Q000097:blood / Q000453:epidemiology / Q000382:microbiology*; D013212:Staphylococcus epidermidis / Q000201:enzymology / Q000302:isolation & purification*